Low expectations can be a blessing. Consider Dae-Sung Koo of the New York Mets, standing at second base at Shea Stadium on a Saturday afternoon. Koo, a 36-year-old rookie relief pitcher out of the Asian professional leagues, had just swung a bat for the first time ever in a major-league game-clubbing a pitch from Yankees ace Randy Johnson over the drawn-in outfielders for an easy double.

That wasn’t even the good part: Jose Reyes, batting next, laid down a sacrifice bunt. Yankee catcher Jorge Posada charged up the first-base line, grabbed the ball, and threw it to Tino Martinez at first base. Koo, advancing to third base, got an idea. “I just noticed,” he said after the game, through an interpreter, “that the pitcher and catcher were actually closer to first base.”

“All of a sudden,” outfielder Mike Cameron marveled in the Mets locker room, reliving the moment, “he’s sprinting to the house.”

Martinez, incredulous, fired back to Posada, in full retreat. The catcher applied a sweeping tag as Koo slid into home, fading away, his fingertips stretching for the plate. Technically, on replay, the tag seemed to get him. The umpire saw otherwise. The Mets led 3-0, on their way to a 7-1 victory.

“If he said ‘safe,'” Koo said, when asked if the call had been correct, “isn’t the guy safe?”

What you get, in baseball, is what you get. In the past weekend’s collision of the Yankees and the Mets, you got a split decision in favor of the Yankees. But not by much.

The Yankees, after Sunday, had won 12 of their last 14 games. They had scored the most runs in the majors. The Mets had done neither. Yet the Flushing team and the Bronx one had the same record, at 23 and 21.

And the larger question is, who would you rather be, on the edge of summer in 2005? The Mets are young and erratic and haven’t been to the playoffs since 2000. The Yankees are old and erratic and have been to the playoffs every year-but they haven’t won a World Series since they beat the Mets, in 2000.

“Two hundred million doesn’t go as far as it used to,” a fan in a Tom Seaver shirt crowed Sunday afternoon, after the Mets had taken an early lead. The key play had been Alex Rodriguez, the Yankees’ $250 million shortstop-cum-third-baseman, booting a two-out ground ball off the bat of Pedro Martinez, the Mets $53 million starting pitcher. As the ball bounced away, a clamor of pure sarcastic noise rose from the stands, subsiding into chants of “A-Rod! A-Rod!”

Rodriguez leads the majors in home runs and R.B.I., including a record-breaking three-home-run, 10-R.B.I. night in the Bronx earlier this year. Still, somehow, he reeks of failure. This year, he has been the worst defensive third baseman in the majors. In the Saturday game at Shea, he leaned too far off first base on a pitch in the dirt and got picked off-a graceless, humiliating pickoff, his gait falling apart as he tried to run in two directions at once, knees pumping, with great staggering clown strides. Earlier this year, at Yankee Stadium, a home fan sang along with “Jumpin’ Jack Flash”: “It’s allll-riiight / ‘Cause A-Rod sucks a bigfatdick.” Little-boy Met fans call him “Gay-Rod.”

How can the richest-and still possibly the greatest-player in baseball be such a sad sack? He is essentially a piece of surplus. In exchange for the chance to be a World Champion Yankee, he broke off a career as the best shortstop ever. He settled for a lesser position, third base, yielding the toughest spot on the field to Derek Jeter. It was, on some fundamental level, a chump move.

And there has been something chumpy and clunky about the Yankees as a team this season. Their offense is built, under impeccable modern-baseball reasoning, around patience and slugging. They work the count, take walks and wear out pitchers. When they get going, they’re a steamroller.

The Mets’ offense, on the other hand, is defective in theory, and often in games. Their shortstop and leadoff man, Jose Reyes, is all but incapable of drawing a walk. Their principal second baseman, Kazuo Matsui, can’t walk either, and is nearly an automatic out. They are not afraid to hack away, and they do.

But against the Yankees’ Randy Johnson, the Mets’ unsound aggression was exactly what worked. Reyes, leading off the game, lashed a ball off Johnson for an infield hit. The following hitters, swinging early, sprayed hits everywhere: lining the ball hard to all fields, blooping it, pounding it to the ground for a high-bouncing Baltimore chop. The Mets had 12 hits off Johnson and a 4-0 lead, while the Yankees still waited to score.

Part of the Yankees’ troubles, too, is that walks and home runs are among the last skills that aging ballplayers lose. And the Yankees aren’t really aging-the Yankees are aged.

When people say a team has holes in it, they’re usually speaking figuratively. But the holes in the Yankees are visible physical spaces: the alleys in right- and left-center; the circles of no-man’s land behind the infield; the faraway arc by the fence line in deep center field, where Dae-Sung Koo deposited his double.

The Yankees had a chance to shore up their defense in the off-season. Carlos Beltran, the Houston Astros’ then-27-year-old star center fielder, was becoming a free agent. But they chose to spend their money on pitchers instead, and Beltran landed with the Mets.

The decision was a rare failure of Yankee ruthlessness: They passed up the available superstar to save center field for the veteran Bernie Williams and the money for Randy Johnson. But Williams, fading, is now on part-time duty anyway. Hideki Matsui, shifted from left field, is working center most days, with Tony Womack, at age 35, trying to learn to play left.

However the players are deployed, the average Yankee is 34 years old. Opposing teams have been merciless about the Yankees’ shortcomings, particularly in the outfield. They hit the ball in the gap and assume the best, hitting second base in full stride, digging for a triple.

“It’s exciting,” Mets manager Willie Randolph said after Saturday’s game, in which Reyes had hit one over Bernie Williams’ head and sped around to third base. “He’s beautiful to watch.”

But youth has its limitations. On Sunday afternoon, with the Mets leading 3-1 and five outs from winning the series, 22-year-old third baseman David Wright-who had dived into the stands to catch a foul ball with the bases loaded earlier-allowed the Yankees’ Tony Womack to reach on an error. The next batter hit a perfect double-play ball to second base. Miguel Cairo flipped it toward Reyes, and the 21-year-old acrobat made an awkward backward pirouette, ending with the ball bouncing away.

Error. The runners were safe. Three batters later, after a two-run single by Hideki Matsui and a double by Williams, the Yankees led.

Afterward, the Yankees hailed the game as a turning point. “That’s why you play nine innings,” Rodriguez said. ” … The team showed a lot of heart today.” So far, though, the Yankees season has been one turning point after another: the 13-run inning, after George Steinbrenner chewed them out; the 11-1 win over Texas, after Jeter chewed them out; Rodriguez’s big night; Bernie Williams’ grand slam. And all the Jason Giambi noise. With patience, everything will get better. By most accounts, everything does keep getting better.